One dominant body at a time
Real spacecraft are tugged by every nearby object: a moon, its planet, the star, and even more distant bodies, though their pulls vary in strength. Calculating all those influences together is called an n-body problem. In many situations, the combined tugs make a spacecraft’s path complicated to predict exactly.
Kerbal Space Program simplifies the math with a method called patched conics. It treats a ship as orbiting just one dominant body at a time. Near a planet, the planet sets the ship’s orbit; once the ship enters a moon’s sphere of influence—the region where the moon is treated as the main gravitational influence—the game switches to a moon-centered orbit.
Why the switch matters
Each segment is a conic section, a family of smooth curves that includes circles, ellipses, parabolas, and hyperbolas. The game can calculate those segments efficiently and show them as a clear projected path. That makes it practical to plan a burn, see where a craft will go, and recognize when it will encounter another body.
The simplification also makes the boundary between influences unusually crisp. In reality, a planet’s pull does not suddenly vanish at a moon’s sphere of influence; the moon’s and planet’s tugs overlap continuously. KSP’s orbit prediction instead joins one simplified path to the next when the ship crosses that boundary.
The payoff is legibility: players can plan interplanetary journeys using a readable chain of orbits and encounters, rather than tracking a constantly shifting web of gravitational pulls. The path is an approximation, but one designed to make the consequences of a spacecraft maneuver visible and manageable.
